Membrane external-cavity surface-emitting lasers (MECSELs) are a new kind of vertically-emitting semiconductor laser with enormous potential and versatility for tailoring the laser parameters. Part of their benefits is related to the fact that they do not need to employ integrated distributed Bragg reflectors (DBRs), which are known to hamper the heat transfer and limit wavelength versatility via strain and band-gap engineering constraints. Furthermore, the substrate on which the active region is grown on is removed and the resulting thin active region membrane is sandwiched between transparent intra cavity (IC) heat spreaders for improved thermal management. Initial characterization of room temperature operation of a new red-emitting AlGaInPbased structure design containing 40 quantum wells (QWs) will be presented. Further, the main aspects of the design of active region membranes will be reviewed with respect to double-side pumping possibilities enabled by the absence of a DBR and the substrate. The comparably high cavity losses show future potential of a properly double-side pumped gain structure.